GENERAL TECHNIC 13 



mens can be readily re-embedded by dissolving out the old celloidin 

 with alcohol and ether and putting them again thiough the regular 

 embedding process. If blocked specimens are kept in equal parts 

 alcohol and glycerin, the celloidin will retain its toughness for months 

 or even years. 



(2) Clove-oil Celloidin. — A more rapid impregnation of the 

 tissue may be obtained by means of what is known as clove-oil cel- 

 loidin. 



Celloidin, 30 gm. 



Clove oil, 100 c.c. 



Ether, 400 c.c. 



Alcohol, absolute, 20 c.c. 



The celloidin is first placed in a jar and the clove oil and ether added. 

 From two to four days are required for solution of the celloidin. 

 During this time the jar should be shaken several times. After the 

 celloidin is dissolved the absolute alcohol is added and the solution 

 is ready for use. 



The specimen must be thoroughly dehydrated, placed in alcohol 

 and ether or pure ether for a few hours, and then transferred to the 

 clove-oil celloidin . From six to twelve hours is sufficient to impreg- 

 nate small pieces of tissue. The tissue is now taken from the cel- 

 loidin, placed directly upon a wooden or vulcanized block, and im- 

 mersed in chloroform. The celloidin hardens in about an hour, and 

 is then ready for sectioning. The specimen is very firm, and very 

 thin sections can be cut. 



A disadvantage in clove-oil celloidin is that neither the blocks nor 

 the sections can be kept permanently in alcohol, as can those embedded 

 in alcohol-ether celloidin. They may. however, be kept for several 

 weeks in pure chloroform. 



Paraffin Embedding 



For paraffin embedding a thermostat or paraffin oven is necessary 

 in order that a constant temperature may be maintained. The tem- 

 perature should be about 56° C. Pure paraffin, the melting-point 

 of which is from 50° to ss° C., is used. In very warm weather it 

 may be necessary to add to this a little paraffin, the melting-point of 

 which is 62° C. 



The hardened tissue is first put in 96-per-cent. alcohol for from 

 twelve to twenty-four hours, and then completely dehydrated by put- 

 ting in absolute alcohol for the same length of time, or less for small 



